Optical coherence tomography (OCT) and, in particular, Fourier domain optical coherence tomography (FDOCT) is a standard of care in clinical ophthalmology. FDOCT systems acquire images of translucent structures rapidly and at high resolution, but have limited imaging depth due to optical constraints. For these reasons, among others, FDOCT is widely adopted for imaging of the retina where the necessary depth of field is limited, but use in refractive applications involving the entire refractive structure of the eye remains still developing.
Low coherence interferometry (LCI), the non-scanning analog of OCT, is commonly used in ocular biometry to measure distance between optical surfaces of the eye. This application is important to planning of refractive and cataract surgery, and to the prescription of replacement lens used in cataract surgery. These measurements are accurate and rapid, but are not typically combined with imaging and, thus, have limitations in utility and may not fully exploit the volumetric imaging capabilities of LCI, OCT and FDOCT.
Corneal topographers are able to measure the shape of the front, or anterior surface of the eye using the distortion of a pattern reflected from the cornea. Approximations are used to compute refractive parameters of the eye based on these front surface images.
Computational OCT has recently been applied to imaging both the front and back surfaces of the cornea to improve the accuracy of refractive computations, and to couple refractive analysis with structural imaging. This technique has been applied to the cornea, but neglects the lens of the eye.
Wavefront aberrometry is often used to compute the functional refractive state of the eye. This technique detects a wavefront reflected from the retina. The refractive output can be accurate, but the results do not inform the user on the origin of any aberrations or contributions to refractive power.
FIGS. 1A-1C are images illustrating a series of inner eye lid images obtained using Spectral Domain Ophthalmic Imaging System provided by Bioptigen, Envisu™ R2300. FIG. 2 is an image obtained using a full range anterior segment Spectral Domain Optical Coherence Tomography (SDOCT) system with a 7.5 mm depth of view with telecentric imaging optics. FIGS. 3A through 3I are a series of images obtained using a traditional SDOCT system with telecentric imaging optics.
A technique for obtaining an image of extended structures of the eye, suitable for computing the refractive properties of the eye and measuring axial and lateral distances of the eye has the potential to provide all of the benefits of LCI, OCT, topography, and aberrometry in one consolidated instrument.